Comparative Analysis of Physiological, Enzymatic, and Transcriptomic Responses Revealed Mechanisms of Salt Tolerance and Recovery in Tritipyrum

Salt stress results in the severe decline of yield and quality in wheat. In the present study, salt-tolerant Tritipyrum (“Y1805”) and salt-sensitive wheat “Chinese Spring” (“CS”) were selected from 121 wheat germplasms to test their physiological, antioxidant enzyme, and transcriptomic responses and mechanisms against salt stress and recovery. 56 chromosomes were identified in “Y1805” that comprised A, B, and D chromosomes from wheat parent and E chromosomes from Thinopyrum elongatum, adding to salt-tolerant trait. Salt stress had a greater inhibitory effect on roots than on shoots, and “Y1805” demonstrated stronger salt tolerance than “CS.” Compared with “CS,” the activities of superoxide dismutase and catalase in “Y1805” significantly increased under salt stress. “Y1805” could synthesize more proline and soluble sugars than “CS.” Both the net photosynthetic rate and chlorophyll a/b were affected by salt stress, though the level of damage in “Y1805” was significantly less than in “CS.” Transcriptome analysis showed that the differences in the transcriptional regulatory networks of “Y1805” were not only in response to salt stress but also in recovery. The functions of many salt-responsive differentially expressed genes were correlated closely with the pathways “peroxisome,” “arginine and proline metabolism,” “starch and sucrose metabolism,” “chlorophyll and porphyrin metabolism,” and “photosynthesis.”

Genome-wide identification, characteristics and expression of the prolamin genes in Thinopyrum elongatum

Background Prolamins, unique to Gramineae (grasses), play a key role in the human diet. Thinopyrum elongatum (syn. Agropyron elongatum or Lophopyrum elongatum), a grass of the Triticeae family with a diploid E genome (2n = 2x = 14), is genetically well-characterized, but little is known about its prolamin genes and the relationships with homologous loci in the Triticeae species. Results In this study, a total of 19 α-gliadin, 9 γ-gliadin, 19 ω-gliadin, 2 high-molecular-weight glutenin subunit (HMW-GS), and 5 low-molecular-weight glutenin subunit (LMW-GS) genes were identified in the Th. elongatum genome. Micro-synteny and phylogenetic analysis revealed dynamic changes of prolamin gene regions and genetic affinities among Th. elongatum, Triticum aestivum, T. urartu and Aegilops tauschii. The Th. elongatum genome, like the B subgenome of T. aestivum, only contained celiac disease epitope DQ8-glia-α1/DQ8.5-glia-α1, which provided a theoretical basis for the low gluten toxicity wheat breeding. The transcriptome data of Th. elongatum exhibited differential expression in quantity and pattern in the same subfamily or different subfamilies. Dough rheological properties of T. aestivum-Th. elongatum disomic substitution (DS) line 1E(1D) showed higher peak height values than that of their parents, and DS6E(6D) exhibited fewer α-gliadins, which indicates the potential usage for wheat quality breeding. Conclusions Overall, this study provided a comprehensive overview of the prolamin gene family in Th. elongatum, and suggested a promising use of this species in the generation of improved wheat breeds intended for the human diet.

Comparison of productivity elements of recombinants of spring bread wheat with translocation from Thinopyrum elongatum carrying rust resistance genes

There have been presented the results of a comparative estimation of recombinants developed on the basis of two commercial varieties (‘Sibirskaya 17’ and ‘Novosibirskaya 31’) hybridized with ‘Thatcher Lr19’ and ‘Thatcher Lr24’. Recombinants were evaluated in the field conditions in 2016, 2017 and 2020. The purpose of the current study was to identify the effect of translocations from Thinopyrum elongatum on the manifestation of productivity elements in recombinants of spring bread wheat developed on the basis of two commercial varieties. The analysis of the genetic composition of the Puccinia triticina populations in Western and Eastern Siberia did not identify genes which were virulent to resistance genes Lr19, Lr24, Lr28, Lr41, Lr47, Lr45 LrSp, Lr6Agi 1 and Lr6Agi 2. The recombinants developed on the basis of the variety ‘Sibirskaya 17’ (the variety productivity was 398.3 g/m2 , grain weight per head was 1.35 g, 1000-grain weight was 37.8 g) were characterized by the severity of the main agronomically valuable traits at the level of the recipient variety, or significantly lower (productivity was 271.5–327.8 g/m2 , grain weight per head was 1.03–1.16 g, 1000-grain weight was 32.5–36.4 g). The recombinants carrying translocations (the length of the period ‘sprouts-heading’ was 44.4 and 44.5 days, grain weight per head was 1.20 and 1.24 g) developed on the basis of the variety ‘Novosibirskaya 31’ (with 42.4 days, 1.02 g) have demonstrated a significant increase in the length of the period ‘sprouts-heading’ and grain weight per head in comparison with the recombinants without translocations (41.6 and 43.6 days, 0.99 and 1.10 g). On average over 3 years, 12 recombinants hybridized from the combination ‘Novosibirskaya 31 x Thatcher Lr19’ produced higher yields (355.6–427.5 g/m2) than those of the recipient variety (301.5 g/m2), both with (6 pcs.), and without (6 pcs.) a translocation.

A recombined Sr26 and Sr61 disease resistance gene stack in wheat encodes unrelated NLR genes

The re-emergence of stem rust on wheat in Europe and Africa is reinforcing the ongoing need for durable resistance gene deployment. Here, we isolate from wheat, Sr26 and Sr61, with both genes independently introduced as alien chromosome introgressions from tall wheat grass (Thinopyrum ponticum). Mutational genomics and targeted exome capture identify Sr26 and Sr61 as separate single genes that encode unrelated (34.8%) nucleotide binding site leucine rich repeat proteins. Sr26 and Sr61 are each validated by transgenic complementation using endogenous and/or heterologous promoter sequences. Sr61 orthologs are absent from current Thinopyrum elongatum and wheat pan genome sequences, contrasting with Sr26 where homologues are present. Using gene-specific markers, we validate the presence of both genes on a single recombinant alien segment developed in wheat. The co-location of these genes on a small non-recombinogenic segment simplifies their deployment as a gene stack and potentially enhances their resistance durability.

Genome-wide Identification, Expression, Characteristics of the Prolamin Superfamily in Thinopyrum Elongatum and Its Kneading Performance in Common Wheat

Background: Prolamins, unique to Gramineae (grasses), play a key role in the human diet. Thinopyrum elongatum (also known as tall wheatgrass, rush wheatgrass, or Eurasian quackgrass) of Elytrigia is genetically well-characterized, but little is known about its prolamin genes and the relationships with homologous loci in the Triticum genus.Results: In this study, a total of 19 α-gliadin, 9 γ-gliadin, 19 ω-gliadin, 2 high-molecular-weight glutenin subunit (HMW-GS), and 5 low-molecular-weight glutenin subunit (LMW-GS) genes in the Th. elongatum genome were annotated. The transcriptome data of Th. elongatum exhibited differential expression in quantity and pattern in the same subfamily or different subfamilies. In addition, microsynteny and phylogenetic analysis revealed dynamic changes of prolamin gene region and genetic affinities among Th. elongatum, T. aestivum, T. urartu, and Aegilops tauschii. The E genome, like the B genome, only contained DQ8-glia-α1/DQ8.5-glia-α1, which provided a theoretical basis for the study of celiac disease (CD). Dough rheological properties of T. aestivum-Th. elongatum disomic substitution (DS) lines 1E(1A), 1E(1D), and 3E(3A) showed much higher peak height values than that of their parent.Conclusions: Overall, this study provides a comprehensive overview of the prolamin gene superfamily in Th. elongatum, and suggests a promising use of this species in the generation of improved wheat breeds intended for the human diet.

Introgression of Thinopyrum elongatum DNA fragments carrying resistance to fusarium head blight into Triticum aestivum cultivar Chinese Spring is associated with alteration of gene expression.

The tall wheatgrass species <i>Thinopyrum elongatum</i> carries on the long arm of its chromosome 7E a locus contributing strongly to resistance to fusarium head blight (FHB), a devastating fungal disease affecting wheat crops in all temperate areas of the world. Introgression of <i>Th. elongatum</i> 7E chromatin into chromosome 7D of wheat was induced by the <i>ph1b</i> mutant of CS. Recombinants between chromosome 7E and wheat chromosome 7D, induced by the <i>ph1b</i> mutation, were monitored by a combination of molecular markers and phenotyping for FHB resistance. Progeny of up to five subsequent generations derived from two lineages, 64-8 and 32-5, were phenotyped for FHB symptoms and genotyped using published and novel 7D- and 7E-specific markers. Fragments from the distal end of 7EL, still carrying FHB resistance and estimated to be less than 114 and 66 Mbp, were identified as introgressed into wheat chromosome arm 7DL of progeny derived from 64-8 and 32-5, respectively. Gene expression analysis revealed variation in the level of expression of genes from the distal ends of 7EL and 7DL in the introgressed progeny. The 7EL introgressed material will facilitate use of the 7EL FHB resistance locus in wheat breeding programs.

Transfer of Fusarium Head Blight Resistance from Thinopyrum elongatum to bread wheat cultivar Chinese Spring

The diploid form of Tall Wheatgrass, Thinopyrum elongatum (Host) D. R. Dewey (2n = 2x = 14, EE genome) has a high level of resistance to Fusarium head blight. The symptoms do not spread beyond the inoculated floret following point inoculation. Using the series of E genome chromosome additions in a bread wheat cultivar Chinese Spring (CS) background, the resistance was found to be localized to the long arm of chromosome 7E. CS mutant ph1b was used to induce recombination between chromosome 7E, present in the 7E(7D) substitution and homoeologous wheat chromosomes. Multivalent chromosome associations were detected in BC1 hybrids attesting to the effectiveness of the ph1b mutant. Genetic markers specific for chromosome 7E were used to estimate the size of the 7E introgression in the wheat genome. Using single sequence repeat (SSR) markers specific for homoeologous wheat chromosome 7, introgressions were detected on wheat chromosomes 7A, 7B and 7D. Some of the introgression lines were resistant to Fusarium head blight.

Origins and chromosome differentiation of Thinopyrum elongatum revealed by PepC, Pgk1 genes and ND-FISH

<i>Thinopyrum elongatum</i> is an important gene pool for wheat genetic improvement. However, the origins of the <i>Thinopyrum</i> genomes and the nature of the genus’ intraspecific relationships are still controversial. In this study, we used single-copy nuclear genes and non-denaturing fluorescence <i>in situ</i> hybridization (ND-FISH) to characterize genome constitution and chromosome differentiation in <i>Th. elongatum</i>. According to phylogenetic analyses based on <i>PepC</i> and <i>Pgk1</i> genes, there was an E genome with three versions (E^e, E^b, E^x) and St genomes in the polyploid <i>Th. elongatum</i>. The ND-FISH results of pSc119.2 and pAs1 revealed that the karyotypes of diploid <i>Th. elongatum</i> and <i>Th. bessarabicum</i> were different and the chromosome differentiation occurred among accessions of the diploid <i>Th. elongatum</i>. In addition, the tetraploid <i>Th. elongatum</i> has two groups of ND-FISH karyotype, indicating that the tetraploid <i>Th. elongatum</i> might be a segmental allotetraploid. In summary, our results suggested that the diploid <i>Th. elongatum</i>, <i>Th. bessarabicum</i> and <i>Pseudoroegneria</i> were the donors of the E^e, E^b and St genome to polyploid <i>Th. elongatum</i> species, respectively.